An aromatic hydrocarbon resin, which is obtained by reacting a polycyclic aromatic hydrocarbon including, as a main component, an alkylnaphthalene such as methylnaphthalene and/or a dialkylnaphthalene such as dimethylnaphthalene, and paraformaldehyde in the presence of an aromatic monosulfonic acid, has been conventionally known as a resin excellent in compatibility with an epoxy resin and the like and solubility in an organic solvent such as xylene (see Patent Literature 1). A phenol resin, which is obtained by reacting a methoxymethylene naphthalene compound and a compound having a phenolic hydroxyl group, such as phenol, cresol or naphthol, in the presence of diethyl sulfate, and has a structure in which naphthalene and the compound having a phenolic hydroxyl group bind to each other via a methylene group, has also been known as a resin for an epoxy resin-curing agent, having a good moldability and the like (see Patent Literature 2).
A method for providing a modified dimethylnaphthalene formaldehyde resin having high heat resistant by modifying a dimethylnaphthalene formaldehyde resin with naphthols or phenols has also been known (see Patent Literatures 3 and 4).
As other polycyclic aromatic hydrocarbon, for example, an acenaphthene resin having a unit structure represented by the following formula has been known (see Patent Literature 5).

wherein R1 represents a monovalent atom or group and k represents an integer of 0 to 4, provided that when k represents 2 to 4, a plurality of R1 may be the same or different; and R2 to R5 independently represent a hydroxy group, or a monovalent atom or group.
Furthermore, a method for producing a polycyclic aromatic condensate, including condensing a polycyclic aromatic hydrocarbon and formaldehyde in the presence of an acid catalyst, and then condensing the resultant by an aromatic hydrocarbon having a hydroxyl group or the like (see Patent Literature 6), and a naphthalene-based oligomer having a high refractive index, obtained by condensing naphthalenes and formaldehydes in the presence of an acid catalyst (see Patent Literature 7) have also been known.
In addition, a method for treating an aromatic hydrocarbon formaldehyde resin, including heating an aromatic hydrocarbon formaldehyde resin in the presence of an acid catalyst, and blowing steam thereto to reduce the number of acetal groups in the aromatic hydrocarbon formaldehyde resin (see Patent Literature 8), and a method for producing an aromatic hydrocarbon phenol resin, including reacting phenols and an aromatic hydrocarbon aldehyde resin using phosphoric acids for a catalyst (see Patent Literature 9) have also been known.